Method of making gaseous glow tubes



March 28, 1961 J. H. Mcc u 2,977,176

METHOD OF MAKING GASEOUS GLOW TUBES Filed Feb. 13, 1959 ASSEMBLE TUBE SEAL REVERSE PROCESS BAKE ALL AND CATHODES EXHAUST GLOW CATHODES F I g 6 LOW INVENTOR. SEPARATELY JOHN H. Mc CAI/LE) BY; 6 Fig. 2

A TTORNE Y rates 2,977,176 METHOD on MAKING GASEQUS GLOW TUBES John H. McCauley, Elizabeth, N.J., asnignor to Burroughs Corporation, Detroit, Mich., a corporation of Michigan Filed Feb. 13,1959, Ser. No. 793,188 7 Claims. cram-2e of cathode indicator glow electrodes and a gas suitable for supporting cathode glow. When a suitable electrical potential is applied between. the anode and a cathode electrode, the cathode lows and space current flows through the gas from the cathode to the anode. The cathodes generally include a' main body portidn in the form or a numeral, letter, or the like, and a lead wire which is connected to one of the tube pins or prongs within the tube envelope. Since each cathode and its ladis, in eifect, one contiriuo'us elect-rode, if the lead and its pin are not coated with an insulating material, these parts may glow when the main body of the cathode glows. Since, for many r asons, it is desirable to use uncoated lead wires and pins, a problem arises concerning the selective processing of the cathodes and their leads and pins to insure that only the main body of each cathode glows and not the leads and pins.

Accordingly,the objects of the present invention cohcer'n the provision of improved gaseous glow tubes and animp'ro-ved method or making the same. I p

In brief, a method of preparing a 'gaseoiis indicater glow tube, according to the invention, relates particularly to the aging process and is employed after cathode and anode electrodes are mounted in an envelope which is evacuated and filled with a suitable gas under pressure. The aging process 'of the invention is particularly eirective in a tube in which the anode is a comparatively large-area electrode and in which a shield means is provided between the main body portions of the indicator glow cathodes and the leads and pins connected thereto. The aging process of the invention includes first the step of applying a larger than normal activating voltage aiid current between the anode 'aiid all of the oathodes simultaneously so that allof the cathodes glow. The next step comprises cyclically turning oii each of the cathodes in order for a short time. Under some circumstances, it may also be desirable to utilize, as a first or preliminary step, a reverse processing operation in which the anode is operated as a cathode and glows, and the cathodes are operated as an anode and d'ci'not glow.

The invention is described in greater detail byreference to the single sheet of drawings wherein:

Fig. l is a perspective view, partly in section, of a gaseous indicator tube prepared according to the method of the invention; and

Fig. 2 is a flow chart of the steps of the method of theinventiori. .7

Referring to the drawings, a typical gaseousindicator glow tube 1i) prepared according to the invention inchides an envelope 12 which has been evacuated (if an and filled'wlth a gas siich as neon or the like at a suit atent C numbers, ten of suchelements are provided, including; Fewer than ten cathodes are able pressure to sustain cathode glow. The ressure may be about 60 mm. of Hg. The envelope includes a base portion, or stem 14, through which metal base pins or prongs 16 extend and by means of which el trical connection is made to suitable external electrical circuit elements. To diametrically opposed pins 16 are adapted to receive and support the various electrode elements of the tube and are providedwith a suitable insulating coating (not shown). The envelope manein cludes a transparent viewing window 29 through which glowing indicator cathode electrodes 22 are viewed. -A sealed off exhaust tubulation (not shown) is provided in the stem 14. 1

The indicator cathode electrodes 22 of the tube 10min" take substantially any desired shape; for example, they may be numbers, letters, or the like, and they may be as few in number as desired, or as many as is pr at for the size. of the tube. Such cathodes are compara tively fragile and have small surface areas. In ane form of the tube 10 wherein the cathode elements are the numbers 0 to 9. shown in Fig. l for purposes of simplification of the drawing. The cathode elements 22 are "made of any suitable metal, for example, stainless steel, aluminum, Nichrome, molybdenum, or the like, and they may be made in any suitable fashion, for example, by etching, stamping, or the like. The present invention permits the use of indicator cathodes 22 having apertured tabs 23 integral therewith by means of which they are mounted and supported on the elongated pin's or posts 16'. The cathode elements 22 are stacked on the posts 16' one above the other with their surfaces oriented parallel to each other transverse to the vertical axis of the tube and facing; the viewing window 20 of the envelope 1'2; Tnecathode elements 22 are mounted with suitable in sulating spacers 2*4 threaded on the posts 16' between" them the spacers being larger than the a'pertur'ed tabs 23 and'having suihcient surface area to cover and insulate the tabs to prevent them from glowing. The stack of electrodes is locked on the posts by mica rings 26, or the like. 7

Each cathode indicator element is provided with a fine wire connectinglead 28 which may be integral with A pair of diametrically opposed longitudinal slots 36' and 38 are provided in the wall of the cup adjacent toand aligned with the support posts 16. The base of the cup 30 rests on, but is insulated from, the pins 16 by an insulating disk do of mica or the like. The anode cup is also electrically connected to one of the pins 16 by a suitable lead 42 which passes through an aperture 44in its base 32. j

The cathode lead wires 28 extend from the cathodes through the slots 3s and 3 3 to the pins 1-6. The stack of cathodes is thus, in effect, contained within the cup.' It is desirable, but not necessary, that the cathodes and their tabs and leadsbe arranged so that the leads 2'8 of adjacent cathodes pass through opposite slots to the proper pins. Thus, for example, the lead of the first cathode in the stack is attached to that portion of the cathode which is adjacent to slot 36, and the lead cx- Patented-Mar. as, 1961 3 F of the cathode which is adjacent to the slot 38 and extends through the slot 38 to its pin, and so forth, throughout the stack.

In addition, considering all of the leads which pass through the slot 36, it is desirable, but not necessary, to pass the leads alternately to the right and to the left of the slot to the proper pins. Thus, the lead of the first cathode may pass to the right of the slot; the next may pass to the left of the slot, and so forth, through the stack.

It can be seen that the cup electrode 36 acts as a shield between the main body portion of each cathode electrode 22 and its lead 28 and pin 16. With this arrangement, the anode'cup assists in preventing the pins and leads from glowing when the cathodes glow.

A screen electrode 46 is mounted on the posts 16' at the top of the stack of cathode electrodes. The screen 46 is insulated from the adjacent cathode 22 by means of two of the spacers 24. The screen electrode may be connected to the cup 30 by metal tabs 48 so that it operates as part of the anode of the tube It). The screen electrode 46 also serves to trap metal sputtered by the cathode electrodes and thus prevents such metal from depositing on and clouding the viewing window 20.

According to the method of the invention, the tube 10 is prepared as follows, referring to the flow chart of Fig. 2. First, the cathode indicator electrodes 22, the anode screen 46', and the cup electrode 50 are assembled on the tube stem 14, and the stem and envelope 12,are sealed together. The envelope and its contents are then baked and exhausted according to standard techniques and the envelope is filled with a suitable gas, such as neon, at a suitable pressure, in the range of about to about 100 mm. Hg.

Next, the tube is aged. The aging of gas tubes, essentially, comprises operating the tube electrodes under rather drastic electrical conditions for a comparatively short time. The specific conditions employed in the aging process depend on'several factors including tube size, gas pressure, and electrode sizes and materials. According to the invention, the following aging process was employed with a tube having a height and diameter of about one inch, a gas pressure of about 70 mm. of Hg and stainless steel cathode electrodes of about .015 inch in width and about 0.75 inch in length. In the aging process, first, all of the cathodes 22 are caused to glow at the same time at greater than normal brightness for about one hour. This is achieved by applying a voltage of about 300 volts between the cathode electrodes and the anode electrode and passing a total current of about 30 to 40 milliamperes. Thus, about 3 or 4 milliamperes of current flow per cathode. At the beginning of this operation, some of the tube pins 16 and cathode leads 28 may glow spuriously. However, by the end of the operation, all of such spurious glow has disappeared.

Next, each of the cathode numbers is caused to glow separately and more brightly than normal for about 24 hours with approximately 300 volts applied and about 4 milliamperes of current passed by each cathode. The cathodes are turned on consecutively and each is allowed to glow for a fraction of a second during this processing operation. After this operation has been performed, the cathode electrodes and the gas have been properly aged, and the tube itself is ready for operation.

Under some circumstances, for example, in processing. tubes of other sizes or tubes which utilize cathode electrodes of molybdenum or some other metal, the method of the invention may be varied as follows. After the tube has been assembled and processed as above, up to the point of aging, the aging process is begun with a step which is called reverse processing. In this step, the anode cup is operated as the cathode, and the cathodes are operated collectively as the anode. The electrical parameters for this step comprise an applied voltage of about 300 volts and a total current flow of about l0 milliamperes. This step has a time duration of about minutes, during which the cup electrode, operated as the cathode, glows brightly. Apparently impurities are removed from the gas and are trapped on the relatively large surface area of the cup. When this step is completed, the gas generally glows with its normal characteristic color, a fact which is used as an indicator that the reverse aging step may be discontinued.

After the reverse aging step, the aging process described above is followed. If, during the aging process, the gas appears to assume a glow which is not its normal characteristic color, the above-described reverse processing operation may be employed again to recover the characteristic gas color.

It is clear that other gases than neon, for example, argon, kryptron, or the like, may be used and the gas pressures may be varied within the scope of the invention. In addition, the time periods during which the cathode electrodes are operated and the aging currents and voltages may be varied within the scope of the invention, depending on cathode materials, tube size, and the like. The essence of the method of the invention comprises the inclusion of the steps of aging the cathode electrodes by turning them all on at the same time for a period of time and then operating them consecutively for a period of time.

One advantage of the present invention resides in the fact that the aging process substantially eliminates the spurious glow of the tube pins and the lead wires which are connected to cathode electrodes. Thus, the pins and lead wires need not be coated with insulating material as has generally been required in the past.

Another advantage of the method of the invention concerns the speed with which tubes may now be processed. it has been found that as much as 40 hours of aging time may be saved with the present method over methods previously employed.

, What is claimed is:

l. The method of making a gaseous glow tube of the type comprising an envelope containing a gas for sustaining cathode glow, a plurality of cathode electrodes in the form of characters adapted to glow having leads connected to tube pins and an anode electrode, said method com prising the steps of mounting said cathode and anode electrodes in said envelope, filling said envelope with a gas for sustaining cathode glow, causing all of said cathodes to glow at the same time for a period of time until none of said leads and pins glows although said cathodes glow, and then causing said cathodes to glow separately and consecutively for a period of time until said tube has been substantially completely aged.

'2. The method of making a gaseous glow tube of the type comprising an envelope containing a gas, a plurality of cathode electrodes adapted to glow and an anode electrode, said cathodes being connected to tube pins by means of lead wires, said method comprising the steps of mounting said cathodes and anode electrode in said envelope, filling said envelope with a gas for sustaining cathode glow, causing all of said cathodes to glow at the same time and at greater than normal brightness for a period of time until none of said lead wires and tube pins glows, and then causing said cathodes to glow separately and consecutively for a period of time at greater than normal brightness until the tube has been substantially completely aged.

3. The method of making a gaseous glow tube of the type comprising an envelope containing a gas, a plurality of cathode electrodes adapted to glow, an anode electrode and a plurality of electrode leads and pins, said method comprising the steps of mounting said cathodes and anode electrode in said envelope, filling said envelope with a gas for sustaining cathode glow, causing all of said cathodes to glow at the same time for a period of time until substantially no lead and pin glow are present, and then causing said cathodes to glow separately and consecutively for a period of time.

4. The method of making a gaseous glow tube of the type comprising an envelope containing a gas, a plurality of cathode electrodes adapted to glow and an anode electrode, said method comprising the steps of mounting said cathodes and anode electrode in said envelope, filling said envelope with a gas for promoting the glowing of said cathodes, causing all of said cathodes to glow at the same time for about one hour, and then causing said cathodes to glow separately and consecutively for about 24 hours.

5. The method of making a gaseous glow tube of the type comprising an envelope containing a gas, a plurality of cathode electrodes adapted to glow and an anode electrode, said method comprising the steps of mounting said cathodes and anode electrode in said envelope, filling said envelope with a gas for sustaining cathode glow, operating said cathodes as anode and said anode as a cathode until the gas glows with its normal characteristic color, causing all of said cathodes to glow at the same time for a period of time, and then causing said cathodes to glow separately and consecutively for a period of time.

6. The method of making a gaseous glow tube of the type comprising an envelope containing a gas, a largearea cup-shaped anode, and a stack of cathode glow electrodes each having a lead wire secured to a tube pin, said method comprising the steps of mounting said cup-shaped anode electrode in said envelope, mounting said stack of cathode electrodes within said cup-shaped electrode with said cathode lead wires lying outside of said cup-shaped electrode, filling said envelope with an ionizable gas for providing cathode glow, causing all of said cathodes to glow at the same time for a period of time until none of said cathode lead Wires and tube pins glows while said cathodes glow, and then causing said cathodes to glow individually and consecutively for a period of time until said cathodes have been substantially completely aged.

'7. The method of making a gaseous glow tube of the type comprising an envelope containing a gas, a large-area cup-shaped anode, and a stack of cathode glow electrodes each having a lead wire secured to a tube contact pin, said method comprising the steps of mounting said cup-shaped anode electrode in said envelope, mounting said stack of cathode electrodes within said cup-shaped electrode with said cathode lead wires lying outside of said cup-shaped electrode, connecting each cathode lead wire to a tube pin, filling said envelope with an ionizable gas for providing cathode glow, causing all of said cathodes to glow at the same time for a period of time until substantially all of said cathodes glow but none of said cathode lead wires glows, and then causing said cathodes to glow individually and consecutively for a period of time until said cathodes have been substantially completely aged.

References Cited in the file of this patent UNITED STATES PATENTS 

